Living Environment Regents Practice Test

Why do different body cells of the same individual look and function differently?

1. Different cells are made from different types of proteins

2. Different genes are activated in different kinds of cells

3. Cells have distinct organelles based on their function

4. All cells have the same DNA, hence they are identical

The correct answer is: Different genes are activated in different kinds of cells

The reason why different body cells of the same individual exhibit distinct appearances and functions primarily hinges on the activation of different genes in various types of cells. While all cells in an individual typically have the same DNA, the specific genes that are expressed or activated can vary, leading to the production of different proteins. These proteins then contribute to the unique structural and functional characteristics of each cell type. For example, muscle cells express genes that code for proteins necessary for contraction, while nerve cells express genes related to signaling and neurotransmitter production. The other options do not accurately capture why cell differentiation occurs. For instance, while it is true that cells can be made from different types of proteins, the underlying factor driving this diversity is the selective expression of genes. Additionally, although cells may contain distinct organelles that reflect their functions, the primary reason for their differences lies in gene activation. The notion that all cells have identical DNA is misleading in this context since it doesn't account for how gene expression changes everything about the cells' characteristics and roles in the organism.